Supposing the current to be divided into 7 parts, 4 of these parts would flow in the first conductor 2 in the second and 1 in the third.

The whole current is 42 amperes.

4/7 of 42 = 24.

2/7 of 42 = 12.

1/7 of 42 = 6.

Current in first conductor = 24 amperes. } " " second " = 12 " } Ans.

" " third " = 6 " }

CHAPTER VII

ELECTRICAL AND MECHANICAL ENERGY

The production of electricity is simply a transformation of energy from one form into another, usually mechanical energy is changed into electrical energy and a dynamo is simply a device for effecting the transformation.

Prof. Fessenden truly remarks there are two independent properties of matter--gravity and inertia--and these give two ways of defining force and energy.

It should always be remembered that electricity is something real, although not easily defined. And then, too, while it is not matter and not energy, yet under proper conditions (it having the power of doing work) it is convenient to speak of its performances as electric energy. The following questions and answers, although few in number, may present the subject with clearness.

=Ques. What is energy?=

Ans. Energy is the capacity for doing work.

Steam under pressure is an example, a spring bent ready to be released is another form, again, water stored in an elevated tank has capacity for doing work. These examples ill.u.s.trate _potential energy_, as distinguished from _kinetic energy_.

Potential energy may be defined as _energy due to position_, and kinetic energy, as _energy due to momentum_.

=Ques. What is matter?=

Ans. Matter is anything occupying s.p.a.ce, and which prevents other matter occupying the same s.p.a.ce at the same time.

=Ques. What name is given the smallest quant.i.ty of matter which can exist?=

Ans. The atom.

An atom means that which cannot be cut, scratched, or changed in form and that cannot be affected by heat or cold or any known force; although inconceivably small, atoms possess a definite size and ma.s.s.

=Ques. What is a molecule?=

Ans. A molecule is composed of two or more atoms.

=Ques. What is the behaviour of these minute bodies?=

Ans. They are perpetually in motion, vibrating with incredible velocities.

=Ques. Why at this point are definitions of energy and of matter most useful?=

Ans. Because, as stated, all electric action is an exhibition of energy, and energy must act through matter as its medium.

=Ques. What is the difference between electricity and magnetism?=[8]

Ans. The ultimate nature of neither is known. There are, however, some differences. To sustain a current of electricity requires energy. To sustain magnetism requires no energy. A current of electricity is always accompanied by a magnetic field of peculiar form. Magnetism alone cannot produce electricity. Electricity can do work; but magnetism cannot in the same sense--and alike with electricity, neither can it exist without contact with matter.

=Ques. How is energy transmitted from one part of a material substance to another?=

Ans. Gradually and successively. It requires a medium and also time.

=Ques. What is the princ.i.p.al use or function in mechanics of electricity?=

Ans. It is purely that of transmission. It corresponds to ropes, shafts and fluids as a medium of conveying and translating power or work.

=Ques. What is work?=

Ans. Work is the overcoming of resistance through a certain distance.

As a quant.i.ty of water moving from a higher to a lower level will do work, so also will a quant.i.ty of electricity falling through a difference of potential.

=Ques. How is work measured?=

Ans. In foot pounds.

=Ques. What is a foot pound?=

Ans. The amount of work done in raising a weight of one pound one foot or the equivalent, overcoming a pressure of one pound through a distance of one foot.

=Ques. What is the electrical unit of work?=

Ans. The _volt-coulomb_.

A volt-coulomb of work is performed when one ampere of current flows for one second in a circuit whose resistance is one ohm, when the pressure is one volt.

=The Ampere-Hour.=--A gallon of water may be drawn from a hydrant in a minute, or in an hour; it is still one gallon. So in electricity, a given amount of the current, say one _coulomb_, may be obtained in a second or in an hour.

_The ampere is the unit rate of flow._

What is called the electric current is simply the relation of any quant.i.ty of electricity pa.s.sed to the time it is pa.s.sing; that is

quant.i.ty in coulombs = current in amperes time in seconds, or simply

coulomb = ampere second.

Again:

10 coulombs = 2 amperes 5 seconds = 10 amperes 1 second = 1 ampere 10 seconds, etc.